As optical techniques have been developed, schema of optical paths suitable for DWDM (Dense Wavelength Division Multiplex) communication and an OTN (Optical Transport Network) employing a code error correction technique and the like have been standardized.
In the OTN, while a main stream of a communication core network is changed from audio to data, Ethernet (registered trademark) has been widely used, and therefore, common standards are also changed to cope with Ethernet. Furthermore, transmission capacity is also increased to 10 G, 40 G, and 100 G which is commonly standardized.
Note that, in general, a protection method which employs an LCAS (Link Capacity Adjustment Scheme), which effectively utilizes a band of a ring network system when a network failure has not occurred, and which conducts a protection process when a failure has occurred so that all data is supplied to a transmission destination and a ring apparatus which employs the protection method have been developed (refer to Japanese Laid-open Patent Publication No. 2002-359627, for example).